[Equest-users] Modeling Light Shelves for Reduction inCooling/Heating Load?

[Chris Jones]

I agree, the tool must suit the application.  My 
intended message is that you can use equest for 
daylighting, but you need to be aware that equest 
is will produce the results based on the user's 
input - garbage in, garbage out.  One needs to 
take into account occupant behaviour.  I feel it 
is better to use a equest/DOE2.1 for daylighting 
savings as it captures the actual lighting demand 
peak but I tend to adjust my doe2 models to 
achieve a lighting power reduction similar to 
what you would see if you used the PAF factors listed in Appendix G.



At 05:51 PM 23/08/2010, you wrote:
>It’s not my intent to “take sides” or anything, 
>but a curious reader (me) might ask “What do you use, Chris?”
>
>As I’m pointing out – a saving grace of 
>eQuest/DOE2.2 is that you can spoon-feed 
>whatever scheduling you may have generated in an 
>outside program if you don’t like what you’re 
>seeing.  I understand some distrust eQuest’s 
>results enough to regularly use DAYsim to 
>generate custom scheduling.  In my practice, 
>I’ve found it more time-efficient to work within 
>and around the known limitations of eQuest, for 
>the sort of energy modeling I’m regularly tasked 
>with.  I also prefer to use other software 
>packages to model instantaneous daylighting 
>behavior – anyone interested, see archives.
>
>I do think it’s a bit of a stretch however to 
>claim the hourly modeled daylighting behavior of 
>eQuest is comparably dumbed-down as a blanket 
>percentage reduction, as we do with LPD’s for 
>occupancy sensors under 90.1 (I think that’s 
>what you’re referencing) – eQuest’s current 
>capabilities do allow an end-user to effectively 
>compare multiple custom daylighting control 
>strategies and their resultant effects on the 
>rest of a building’s systems (i.e. 
>heating/cooling) in a time-efficient fashion.
>
>I’m not disagreeing the DOE2.1e algorithms 
>aren’t the best for figuring how many fc are 
>incident in a given space for a given hour, but 
>statements that boil down to “eQuest sucks for 
>daylighting” (for LEED modeling or otherwise) 
>can certainly be misleading.  If you can take 
>what’s known to be inaccurate into account, you 
>can realize eQuest as a pretty useful tool for designing with daylighting.
>
>~Nick
>cid:489575314 at 22072009-0ABB
>
>
>NICK CATON, E.I.T.
>PROJECT ENGINEER
>25501 west valley parkway
>olathe ks 66061
>direct 913 344.0036
>fax 913 345.0617
>Check out our new web-site @ <www.smithboucher.htm>www.smithboucher.com
>
>From: Chris Jones [mailto:cj at enersave.ca]
>Sent: Monday, August 23, 2010 4:03 PM
>To: Nick Caton; equest-users at lists.onebuilding.org
>Subject: Re: [Equest-users] Modeling Light 
>Shelves for Reduction inCooling/Heating Load?
>
>Equest, like DOE2.1e before it provides very 
>generous estimates of the lighting energy saved 
>using daylighting controls.  I believe that 
>taking equest predictions at face value for LEED 
>models would be inaccurately providing more 
>benefit than warranted.  The Appendix G power 
>factor ratings are likely not conservative in 
>some cases.  I wouldn't expect to see any more 
>benefit using equest's daylighting than I would 
>using the Appendix G power factor adjustments.
>
>A paper that attempted to explore various 
>daylighting energy reduction savings modelling 
>strategies.  DOE2.1e and Daysim are the two programs used for the analysis.
><http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/nrcc46761/nrcc46761.pdf>http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/nrcc46761/nrcc46761.pdf
>
>
>At 03:49 PM 23/08/2010, you wrote:
>
>Content-class: urn:content-classes:message
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>
>Perhaps these are the answers you’re seeking:
>1.       Building shades and their respective 
>reflectance properties do affect the modeled 
>behavior of space daylighting systems in eQuest 
>models.  Be sure to pay close attention to all 
>three values (and their associated help files) 
>on the right of the following image – they may 
>all play a part depending on what exactly you’re trying to model.
>[]
>
>2.       Based on your query, a 
>caution:  eQuest’s results do not have any 
>inherent degree of accuracy/in-accuracy with 
>regard to the modeled energy consumption 
>resulting from daylighting controls – that 
>depends pretty much entirely on how closely you 
>define the daylighting systems’ behavior to 
>reality.  If you have a program which you 
>perceive to be producing more accurate hourly 
>percentage consumptions for your spaces, then by 
>all means – there’s nothing stopping you from 
>defining a schedule in eQuest to match the other program’s results.
>
>I expect you mean to say you’re utilizing 
>another program to accurately determine the 
>behavior of daylight in response to 
>adding/modifying light shelves, but if you are 
>indeed using another program to determine annual 
>hourly behavior with a weather file, I’d be very 
>interested to hear more about it!
>
>Best of luck,
>
>~Nick
>
>cid:489575314 at 22072009-0ABB
>
>
>NICK CATON, E.I.T.
>PROJECT ENGINEER
>25501 west valley parkway
>olathe ks 66061
>direct 913 344.0036
>fax 913 345.0617
>Check out our new web-site @ <www.smithboucher.htm>www.smithboucher.com
>
>From: equest-users-bounces at lists.onebuilding.org 
>[ 
>mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nilay R. Desai
>Sent: Monday, August 23, 2010 11:35 AM
>To: equest-users at lists.onebuilding.org
>Subject: [Equest-users] Modeling Light Shelves 
>for Reduction inCooling/Heating Load?
>
>E.G. Would it be accurate to model an external 
>light shelve as a horizontal building shade with 
>a high reflectance value on the skyward facing 
>surface? I understand the day lighting benefit 
>in Equest would be inaccurate, but we are using 
>separate software to obtain accurate day lighting results. Thanks!
>
>
>Nilay Desai
>P  626.351.8881 Ext. 237
><mailto:klowe at tmadtg.com>ndesai at ttgcorp.com
>
>
>
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>
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>
>
>Chris Jones
>14 Oneida Avenue
>Toronto, ON M5J 2E3.
>Tel.  416-203-7465
>Fax. 416-946-1005
>


Chris Jones
14 Oneida Avenue
Toronto, ON M5J 2E3.
Tel.  416-203-7465
Fax. 416-946-1005

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